Previously, several switches have been made which relate in general to electrical circuits whether singular or in a dual assembly in which two different switches are operated independently by means of a common shaft or which can be operated together. In these switches, their exists a stationary stator plate and a movable rotor plate properly positioned to change the electrical connections of the switch contacts by rotational or longitudinal movements of a knob device secured to the common shaft. Thus, a disadvantage arises due to wear of moving parts, namely between the stationary stator plate and the movable rotor plate as the knob device is moved. Another disadvantage inherent to these switches is that many require elaborate provisions be made if they are to intrude into an instrument and occupy significant space. Another disadvantage is that three dimensional cabling is required. Typical of the above described switches are the switches fully described in U.S. Pat. Nos. 3,074,011; 3,181,086; 3,187,118 and 3,207,861 all of which are assigned to the assignee of the present invention. Another type switch apparatus employs its movable and fixed switch contacts on a printed circuit board providing the electrical circuit to which the switch contacts are connected as fully described in U.S. Pat. No. 3,562,464 by Charles Howard Vollum et al and assigned to the assignee of the present invention. Such apparatus, however, requires significant space, and is subject to wear.
The application of encoding-decoding by light source, mask and photoreceptors is also well known in the art. For example, U.S. Pat. No. 3,491,244 by V. E. Stewart, Jr. describes an encoder for use in an automatic remote meter reading system which includes a plurality of photo cells disposed between a pair of coded discs and are arranged to be selectively energized from their opposite sides by individual illuminating means associated with each disc. Typical of the encoders and decoders employing coded discs having light openings in a radial array representative of the binary code, such that the position to which the disc is rotated relative to a fixed light source provides an indication in binary form are taught by U.S. Pat. Nos. 3,489,907; 3,740,721; 3,399,297; 3,237,012; and 3,512,006. Thus a disadvantage is that such use of encoding-decoding by light source, mask and photoreceptors are not applied to a switch.